Add onion, carrots, bell pepper and garlic to a sheet pan lined with parchment paper. Do not use a baking dish because the carrots will not cook fast enough.
Roast veggies for 40-45 minutes, until carrots have softened.
Remove garlic from bulb (I squeezed mine) and add to a blender along with the rest of the ingredients.
Blend sauce until smooth. Pour sauce over your favorite pasta and top with basil. Dig in.
Notes
This makes enough sauce for 1 small box of pasta, so 2-4 servings.